Victoria 1839/43 proof Halfpenny, unusual overdate, struck for proof set

Victoria (1837-1901), Bronzed Proof copper Halfpenny, 1839, 39 of date struck over 43, young filleted head left, W:W. on truncation, date below, legend and toothed border surrounding, VICTORIA DEI GRATIA, rev. struck en medaille, Britannia seated right with trident and shield, legend and toothed border surrounding, BRITANNIAR: REG: FID: DEF: emblems in exergue, weight 9.24g (Peck 1523; S.3949). A couple of small belmishes each side, otherwise toned, practically as struck, the more unusual overdate variety, very rare.